Is it fine for a sister show her boobs to her friends and brother on a dare?

I knew of a girl that was very open minded who showed our friend group her nipple piercings. The thing is her brother is in our friend group. We are in our mid 20s and he is in his early 20s. I mean I won't shame anybody for doing that. It is what it is but how would everyone else feel? Also the context of how it happened was through a drinking game dare where she had to flash as part of the dare and some of the girls asked about her piercings while she was flashing for ten seconds. Her brother didn't really seem to care.
Is it fine for a sister show her boobs to her friends and brother on a dare?
Post Opinion